GB2040056A

GB2040056A - Rail type parallel drafting device

Info

Publication number: GB2040056A
Application number: GB7943226A
Authority: GB
Original assignee: Mutoh Industries Ltd
Current assignee: Mutoh Industries Ltd
Priority date: 1978-12-23
Filing date: 1979-12-14
Publication date: 1980-08-20
Also published as: FR2444572B1; US4312132A; IT7969457A0; DE2951841A1; DE2951841C2; IT1119991B; FR2444572A1; GB2040056B

Description

1 GB 2 040 056 A 1

SPECIFICATION

Rail type universal parallel ruler device The present invention relates to a rail type universal parallel ruler device.

In conventional rail type universal parallel ruler devices, a balance weight travels in a cavity portion of a vertical rail in a direction opposite to a head by interlocking with the shifting of the head. The balance weight with its dead weight contacts the bottom wall surface of the cavity portion, namely the travel path thereof, directly or through a roller, but there exists a drawback that, when the balance weight travels in the cavity portion, frictional noise is 80 derived by contact friction between the balance weight and the bottom wall surface of the cavity portion. Furthermore, when the balance weight travels the side surface of the balance weight contacts the traverse vibration control surface formed in the cavity portion of the vertical rail by the traverse vibration of the balance weight, and noise is derived by this contact, or the movement of the balance weight becomes heavy by the friction caused by the contact, which constitute further drawbacks.

The present invention provides a rail type univer sal parallel ruler device, comprising a drawing board, a horizontal rail mounted on the drawing board, a horizontal cursor mounted shiftably on the 95 horizontal rail, a vertical rail connected to the horizontal cursor and having a weight travel path formed along its longitudinal direction, a vertical cursor mounted shiftably on the vertical rail, a balance weight disposed shiftably on the weight 100 travel path and being connected to the vertical cursor to interlock with the vertical cursor in mutual ly opposite directions, and a head connected to the vertical cursor, wherein one or more magnetic members are disposed over substantially the entire 105 length of the weight travel path, and one or more further magnetic members opposed to the first mentioned magnetic members are mounted at the side of the balance weight, both the said sets of magnetic members being disposed in opposition to 110 work such thatthe balance weight is floated relative to the weight travel path.

By means of the present invention the balance weight may travel smoothly along its travel path by decreasing or eliminating contact friction derived between the balance weight and its travel path by means of the magnetic force causing the balance weight to float on its travel path. It is also possible to decrease or eliminate the noise derived by contact between the balance weight and its travel path.

It is also possible to avoid contact between the balance weight and the side wall surface of the cavity portion of the vertical rail during travel of the balance weight by controlling traverse vibration phenomenon by the magnetic force of the magnets. 125 It is further possible to float the balance weight by repulsion magnetic force working between a plural ity of rows of magnetic pole tracks arranged in parallel in the travel path of the balance weight and a plurality of rows of magnetic pole tracks arranged in 130 parallel at the balance weight side.

Wheneverthe inclined angle of the drawing board is changed, the load of the balance weight perpendicular to its guiding member is changed. For this reason, if the balance weight is floated by the magnetic force, the floating opposed gap between the balance weight and the guiding member is greatly changed by the change of load. As a result, there is derived a drawback that the space for accommodating the balance weight formed in the vertical rail, namely in the guiding member, must be widened. This problem may be overcome by means of the invention by arranging a plurality of rows of magnetic pole tracks in parallel on the opposed portions of the balance weight and the guiding member.

The invention will be further described, by way of example only, with reference to the accompanyir)g drawings, in which:

Figure 1 is a general plan view of a rail type universal parallel ruler device according to the present invention; Figure 2 is a cross-section of a vertical rail of the device shown in figure 1; Figure 3 is a plan view of a vertical cursor of the device shown in figure 1; Figures 4 to 8 are cross-sections showing various embodiments of magnetic floating mechanisms utilized in the vertical rail of the device; Figure 9 is a plan view of the vertical cursor utilized with the embodiment shown in figure 8; Figures 10 and 11 are cross-sections showing other embodiments of magnetic floating mechanisms; and Figure 12 is a graph illustrating the characteristic curves of various magnets.

Figures 1 to 3 show a drawing board 1 fixed to a support frame of a reclining table (not shown) and set at a desired angle between a horizontal orientation and a perpendicular orientation.

A horizontal rail 2 is fixed to the drawing board by means of a vice type fixture, and a horizontal cursor 3 is shiftably connected to the horizontal rail. A vertical rail 4 has one end thereof connected to the horizontal cursor 3, and a tail portion roller 5 is connected rotatably to the other end of the vertical rail. A weight travel path 7 for a balance weight 6 is formed on the vertical rail 4 over its entire length in its longitudinal direction, and a balance weight 6 having a proper weight is shiftably disposed to move along the path 7. The travel path 7 is provided in a cavity portion 8 of the vertical rail 4. A vertical cursor 10 is connected shiftably to the vertical rail 4 by means of a roller 9, and a head 11 is connected to the vertical cursor 10 by means of a hinge. Straightedgqs 12,13 are mounted on the head 11. The vertical cursor 10 and the balance weight 6 are connected by a wire rope 14, and the wire rope 14 is spanned over rope pulleys (not shown) disposed rotatably at both end portions of the vertical rail 4. When the vertical cursor 10 is shifted along the vertical rail 4, the balance weight 6 is interlocked with the shifting of the vertical cursor 10 and is shifted along the cavity portion 8 in a direction opposite to the shifting direction of the vertical 2 GB 2 040 056 A 2 cursor 10. The inertia of shifting of the vertical cursor in a dropping direction along the vertical rail 4 which is derived by the weight of the head 10 when the drawing board 1 is inclined in a rising direction is offset by the inertia caused by the weight of the balance weight, and in the condition where the drawing board 1 is inclined by the offsetting of the inertias, even if the hand is released from the head 11, the head 11 is not dropped along the drawing board 1, and becomes static in a stable mode at a desired position on the drawing board 1.

In Figures 2 and 3, numerals 15,16,17,18 are long magnetic members disposed along almost the entire length of the wall surface of the cavity portion 8, and in this embodiment commercially available man ganese aluminium magnets are employed for the magnetic members 15-18. Magnetic members com prising long magnets 19, 20,21,22,23, 24,25,26 are disposed on the balance weight 6 and these magnets are provided with the polarities shown, and the 85 magnet 15 atthe cavity portion 8 side and the magnet 19 atthe balance weight 6 side are opposed as shown. The magnets 15, 20 and 18,25 perform the operation of floating the balance weight 6 completely in the cavity portion 8 by mutually repulsed magnetic forces. On the magnetic pole surfaces of the magnets 15,18, two rows of magne tic pole tracks of different polarities are formed in parallel. The magnetic pole tracks of the magnets 15, 18 may constitute three rows or four rows, and in essence as long as there are a plurality of rows of pole tracks satisfactory results can be obtained. On the magnets 20, 25, two rows of magnetic pole tracks having different polarities in parallel are formed corresponding to the magnets 15,18. The magnets 16, 21, and 17, 24 perform the operation of maintain ing a gap between the upper surface of the balance weight 6 and the upper wall surface of the cavity portion 8 so that the balance weight 6 does not collide with the upper wall surface of the cavity portion 8 by vibration during travelling of the balance weight 6 in the cavity portion 8. The magnets 15, 19, 18, 26 and 16, 22, 23,17 control the vibration perpendicularto the shifting direction of the balance weight 6 in the cavity portion 8, and perform the operation of preventing the side por tions of the balance weight 6 colliding with the side wall surfaces of the cavity portion 8. On the entire surface of the balance weight 6 is coated a layer 27 of a frictional force decreasing material such as "Tef IoC (Registered Trade Mark). "Teflon" tape 28 is applied on the location of the inner wall surface of the cavity portion 8 which tends to contact the balance weight 6. Also a---TefIoC coating 29 is applied to all the magnets such as the magnet 15.

The balance weight 6 is completely floated in the cavity portion 8 as shown in the drawing by the magnetic force of the respective magnets.

When the vertical cursor 10 is shifted along the vertical rail 4, the balance weight 6 travels quietly and smoothly in the cavity portion 8 of the vertical rail 4 in the completely f loated condition.

When the drawing board 1 is upwardly inclined, for example to an angle of 80' relative to the floor surface from the horizontal, the load from the 130 balance weight 6 applied perpendicular to the travel path 7 of the cavity portion 8 of the vertical rail 4 is greatly decreased in comparison with the condition where the drawing board 1 is in the horizontal orientation. Accordingly, the balance weight 6 is caused to float from the travel path 7 by the magnetic force of the magnets 15,18. However, the amount of floating is minimal in this case, because the magnetic pole surfaces of the magnets 15,18 and 20, 25 are formed by a plurality of rows of magnetic pole tracks. That is, as shown in Figure 12, when the repulsion force is measured along the ordinate and the gap between opposed magnets 82, 84 is measured along the abscissa, in the case where eight rows of magnets 82 are arranged parallel so that mutually different poles are adjacent, and eight rows of magnets 84 are arranged parallel so that mutually different poles are adjacent, and moreover the same poles of the magnets 82, 84 are mutually opposed, the gap repulsion force characteristic becomes a curve 86. Numeral 88 is the characteristic curve in the case where there are four rows of the magnets 82, 84, numeral 90 is the characteristics curve in the case where there are four rows of magnets 90, and numeral 92 is the characteristics curve in the case where there are two rows of magnets 92.

As will be apparent from the foregoing characteristic curves, the greater the number of rows of magnets and the greaterthe magnetic pole tracks, the steeper the characteristic curve becomes. That is, although a bigger repulsion force may be derived, the attenuation of repulsion force against widening of the gap becomes remarkable.

This phenomenon leads to the conclusion that if the load applied to the magnet 82 downwardly is changed to a direction of decreasing the load from the condition where a predetermined load is such thatthe magnet 82 does not contact the magnet 84, the change of gap between the magnet 82 to the magnet 84 is smaller if the number or rows of the magnetic pole tracks of the magnets 82, 84 is increased. This conclusion is obtained from a magnetic flux density distribution characteristics diagram showing the test results by means of a glass meter. That is, as the magnetic member is separated from the magnetic pole surface, the magnetic flux density is attenuated, but the magnetic flux density of a magnet having an increased number of magne- tic pole tracks is remarkably attenuated as compared with a magnet having a decreased number of magnetic pole tracks. Accordingly, if the magnet is floated by the repulsion magnet force relative to the other magnet, and when the load applied from the magnet toward the other magnet is changed from a maximum value to a minimum value, in order to minimize the change of the opposed gap of a pair of magnets, it is better to increase the number of rows of magnetic pole tracks of the magnet in the parallel direction.

During travel of the balance weight 6, it is possible that the balance weight 6 will contact the wall surface of the cavity portion 8, but in this case, as the Teflon members 27, 28, 29 receive the contact, no big frictional load is applied to the travelling of the A a 3 GB 2 040 056 A 3 balance weight 6. As another means of decreasing the frictional force, a roller can be used instead of the Teflon members, for example as illustrated in Figure 4. In Figure 4, a roller 31 is rotatably mounted on a balance weight 30 which is completely floated by the magnetic force of the magnets, in the cavity portion 8, and the surface of the roller 31 is opposed to the upper wall surface and bottom wall surface of the cavity portion with an extremely small gap therebe tween.

When the balance weight 30 travels in a cavity portion 32, and vibration resisting the magnetic force of the magnets occurs, the surface of the roller 31 abuts the wall surface of the cavity portion 32.

Figure 5 shows another embodiment wherein numerals 33, 34 and 35,36 are magnets for floating the balance weight 30 from the bottom wall surface of the cavity portion 32, and mutually the same polarities of the magnets are opposed, and a repul sion magnetic force is derived.

Numerals 33,37, and 35, 38 are magnets for preventing traverse vibration of the balance weight which is completely floated in the cavity portion 32, and the side portions of the balance weight 30 are prevented from contacting the side portions of 90 the cavity portion 32 by the repulsion magnetic force. Numerals 39, 40 are rotatable rollers, and the surfaces thereof are opposed in the proximity of the upper wall surface and bottom wall surface of the cavity portion 32.

Figure 6 shows another embodiment wherein a control rail surface 41 is formed on a travel path 43 in the cavity portion 32 over its entire length in its longitudinal direction, and the control rail surface is in light slidable contact with a traverse vibration control surface 48 of a balance weight 47 which is completely floated in the cavity portion 32 by magnets 42,44 and 45,46. Numerals 49, 50 are rotatable rollers and the surfaces thereof are opposed in the proximity of the travel path 43.

In the foregoing construction, the balance weight 47 travels in the cavity portion 42 by being guided by the control rail surface 41 in the condition where the balance weight 47 is completely floated in the cavity portion 32 by the magnetic force of the magnets 42, 44, and 45, 46.

Figure 7 shows another embodiment wherein traverse vibration control rollers 51, 52 are mounted rotatably on a balance weight 60 which is completely floated in a cavity portion 59 by magnets 55, 56, and 57, 58, and the surfaces thereof are in contactwith the wall surfaces of both sides of the cavity portion 59. Rotatable rollers 61, 62 constitute frictional force decreasing members, and the surfaces of the rollers are opposed in the proximity of the upper wall surface and bottom wall surface of the cavity portion 59.

Figures 8 and 9 show another embodiment where in one end of a balance weight 70 is mounted and contacted on a weight travel path 72 by means of a roller 71 which is a frictional force decreasing member, and the other end thereof is floated relative to the travel path 72 by the repulsion magnetic force of magnets 73, 74. Traverse vibration control rollers 75,76, 77, 78 are mounted rotatably on the balance weight 70, and each surface thereof is in contact with the wall surfaces of both sides of a cavity portion 79.

It will be appreciated that, in practice, the frictional force decreasing members may be other than rollers or Teflon members. Also, the foregoing embodiments utilize the repulsion magnetic force of the magnets, but it is of course possible to float the balance weight by utilizing the attractive magnetic fo rce.

Also, as shown in Figure 10, a space portion 95 for insertion of magnetic members may be formed on the vertical rail 4 made of an aluminium drawn member over its entire length in its longitudinal direction, and magnetic members comprising mag- nets 15,16,17,18, may be press fitted into the space portion 95. Also the cross-sectional shape of the space portion for insertion of the magnetic members may be formed into a shape indicated by numeral 96 in Figure 11. The mounting of the magnetic mem- bers on the vertical rail 4 can be performed easily by the provision of the space portions 95, 96 for insertion of the magnetic members.

Claims

1. A rail type universal parallel ruler device, comprising a drawing board, a horizontal rail mounted on the drawing board, a horizontal cursor mounted shiftably on the horizontal rail, a vertical rail connected to the horizontal cursor and having a weight travel path formed along its longitudinal direction, a vertical cursor mounted shiftably on the vertical rail, a balance weight disposed shiftably on the weight travel path and being connected to the vertical cursor to interlock with the vertical cursor in mutually opposite directions, and a head connected to the vertical cursor, wherein one or more magnetic members are disposed over substantially the entire length of the weight travel path, and one or more further magnetic members opposed to the first mentioned magnetic members are mounted at the side of the balance weight, both the said sets of magnetic members being disposed in opposition to work such that the balance weight is floated relative to the weight travel path.

2. A ruler device as claimed in Claim 1, wherein the balance weight is caused to float relative to the weight travel path by the magnetic force of both the sets of magnetic members.

3. A ruler device as claimed in Claim 2, wherein a frictional force decreasing coating is applied to the balance weight and opposed to the said travel path and/or the surrounding inner wall surface of the vertical rail.

4. A ruler device as claimed in Claim 1, wherein a frictional force decreasing member is disposed on the balance weight and/or the weight travel path, and wherein the balance weight is caused to contact the weight travel path by its dead weight by means of the frictional force decreasing member, and the magnetic force is caused to work on the balance weight in a floating direction relative to the weight travel path.

5. A rulerdevice as claimed in any of Claims 1 to 4, wherein at least one pair of magnetic members is 4 GB 2 040 056 A 4 provided along the weight travel path, and a pair of further magnetic members is provided at the side of the balance weight to be respectively adjacent the said one pair of magnetic members, the said magne- tic members at the weight travel path side and the said magnetic members at the balance weight side being of the same polarity, and the position of the balance weight perpendicular to the longitudinal direction on the weight travel path being controlled by the repulsion magnetic force of the said magnetic members.

6. Arulerdevice as claimed in anyof Claims 1 to 5, wherein the magnetic pole surface of each magnetic member is formed by a plurality of magnetic pole tracks disposed in parallel.

7. Arulerdevice as claimed in any of Claims 1 to 6, wherein a space portion for receiving a magnetic member is formed in the vertical rail over the longitudinal direction thereof, the magnetic member being press fitted into the space portion, and the magnetic member being opposed to the magnetic member provided at the side of the balance weight.

8. A rulerdevice as claimed in any of Claims 1 to 7, wherein the balance weight is connected to the vertical cursor by means of a rope.

9. A ruler device according to Claim 1, substantially as herein described with reference to, and as shown in, Figure 2, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 10 or Figure 11 of the accompanying drawings.

Printed for Her majesty's Stationery Office by Croydon Printing Company Limited, Croydon Surrey, 1980. Published bythe Patent Office, 25Southampton Buildings, London, WC2A lAY, from which copies may be obtained.